Retractable landing gear



April 19, 1949. H ONGE R E 2,467,898

RETRACTABLE LANDING GEAR Filed July 27, 1945 INVENTOR: HENRI LONGEP/EERE Patented Apr. 19, 1949 RETRACTABLE LANDING GEAR Henri Longepierre, Lyons, France; vested in the Attorney General of the United States application July 27, 1943, Serial No. 496,273 In France December 24, 1941 The present invention concerns a raising device for landing gear of aircraft, characterized by the fact that the necessary energy to put successively the landing undercarriage up and down is stored in an energy-accumulator as soon as the landing gear reaches the down position.

Preferably, the accumulator is formed of two elements, one of which supplies the energy for the raising, the second one, the energy for the following depressing of the landing gear, the second element being charged with the energy of the first element during the raising.

The annexed drawing shows several examples of means for realizing the invention. In the various figures of the drawing, the corresponding elements bear the same reference numerals.

In Figure 1, which is a lineal diagram of an example of the invention, the landing gear I, movable around the axis 2, is connected by drive 3, to the first element It of a suitable energyaccumulator of any type whatever (spring, elastic element, screw jack). A motor 5 stores energy in element 4 by means of a drive furnished with a clutch 6, and means connecting the clutch to said energy-accumulator; said means being mechanical, for instance, a drum on which a cable connected to the accumulator is rolled, up or gear elements having a toothed rack connected to the accumulator and united to the driven portion of the clutch. A control member :7 disconnects motor 5 as soon as the energy stored in 4 reaches a sufficient amount. A look device 8 is provided so that the drive 3 and the energy-accumulator 4 are kept in the state in which they were when the energy-accumulator 4 was put under tension. A control member 9, the working of which determines the position of the landing gear undercarriage, engages the clutch when the landing gear reaches the down position. A locking device Hil keeps the landing gear in this position. A second accumulator i 5 (spring, elastic element, screw jack) is provided for the storing, during the raising operation, an amount of energy used for depressing the landing gear.

The working of the device according to the invention is as follows:

As soon as the landing gear reaches the down position, the control member 9 engages the clutch.

5 and the motor '5 operates so as to store energy in the accumulator 4 upito a certain level, at

6 laims. (Cl. 244-102) which level the control member 1 disengages the motor 5. When the aircraft has taken oif and leaves the ground and it is desired to raise the landing gear, it is necessary only to release the locking device Iii. The energy stored in the accumulator 4. is thereby freed and by means of drive 3 causes the raising of the landing gear, the energy stored in accumulator 4 being sufficient to overbalance both the weight of the landing gear and the resistance of the accumulator I l. The lock device it keeps the drive 3 and the energy-accumulator t in the state in which they are when the landing gear reaches its raised position. When it is desired to put the landing gear down, the locking device 8 is released and the energy remaining in the accumulator 4 is thereby freed, and because this energy is no longer suiiicient to overbalance the weight of the undercarriage of the landing gear and the ac-' cumulator H, the landing gear is put down. As soon as the carriage reaches the down position the locking device it works again and holds the undercarriage in said position While the control member 9 lets in the motor clutch 6, and the cycle of the operations described above begins again.

Figures 2 and 3 show two additional embodiments of the invention in which the mechanical energy derived from a motor-driven drum is stored in an elastic element.

In Figure 2, the motor has an electric clutch for driving a drum I 2 on which one end of a cable 13 is wound, the other end of the cable being secured to a thrust block it which engages a control member 1 at a predetermined displacement of the elastic element 5. Clutch 6 and drum I2 are drivably connected by means of gears Ma and 12b. The control member 1 opens the elec-' tric circuit of clutch 6. The thrust block I 4 also has a nipple Ma which may fasten to the locking device 8. The landing gear I is connected by means of the drive 3 to the elastic element 4; it has a contact 9 which in the down position of the landing gear, closes the electric circuit of clutch 6. A wedge i ll, guided by a bearing mounted on the frame of the aircraft and which can be driven into a prepared hole in the undercarriage, constitutes the locking element for the down position. Manually operable means for raising :and

lowering the landing gear is constituted by a lever l5 working by means of drive 16 on the locking devices 8 and it), which devices are releasably held in their locking positions by springs H and I8 respectively, Spring or elastic element H tends constantly to restore the landing gear to the down position.

From Figure 2, the operation of the device shown therein will be clear when it is understood that it shows the undercarriage as it reaches the down position in which, at once, it is locked by wedge l0. To start the device, general switch [9 is closed by hand. Contacts 1 and 9 being closed, the electric clutch is engaged so as to connect the drum' lZ' with the motor so that cable l3'is wound up on the drum, while elastic element 4 elongates. When the thrust of elastic element 4 reaches the position which is represented on the figure in dotted lines, the contact otthe control member 1 opens, thereby openinng'the circuit of the electric clutch B so as to disengagethe motor. At the same time, the nose I la ofth thrust element l4 becomes latched by the locking device 8.

In order to raise the landing gear'undercarriage, the pilot moves the hand lever toward the left, thereby releasing the wedge id from-its hole. The energy stored in the elastic element Q is quickly tr n ormed into tra ers-We s; ac n on drive 3 saiddrive being moved longitudinally whi1e the elastic element 4 gets shorter. The effort exertedby the-elastic element i being greater than thatwhich isexerted-by the elastic element '1 i plus-zthewei ght of the undercarriage, the latter swings-the direction of an arrow. up to the raisedt position in which it may be locked by a suitable means-which'is notshown in the drawing. As" soon' as-thewithdrawal of the wedge iii has freed'mhe undercarriage, the pilot may-let lever lfircome" "back, toits initial or normal position.

'In. order to put the undercarriage down, the pilot-has-only-to move-lever 15 toward the right, whichsputs down :the pawl" 8 and releases the thrust-.-element-l4 of the elastic element i. The elastic element-having no longer a fixed point of support-and the drum 12 being disconnected from the clutch;-the-energy stOredin the elastic element: la'doesnot resist the'pull exerted by elastic element -I I and that'of the weight of=the under carriage; and: therefore the. undercarriage is returned: to its ":down position. The .cycle of operationj-maystart again. Of course, if the undercarriage-gisi-held' in its raised position bya suitablec'locking ='devi c e.- the movement toward :the rightzof lever 15 will free the undercarriage.

I. Eigure 3 shows-adevice-according to the present invention in which thechiefcomponents are the sama-as-thoseot the above-described devices, but in whichmhecontrol system ismechanical. Thus itvwillube sufiicientto give a description of this mechanical control-system; theoperation otherwise being identical to, that which has previously been described. The clutch 6 is mechanically operated-by means of' a bell crankle'ver 29: move ableuaround an axis 2!. Lever is 'worked in a direction'iwhichcauses'engagement of the clutch, by-"means ofnanrelastic' thrust element fixed to the undercarriage and" working. when, the undercarriage has reachedits down position. The torque ofathe'motor 5 is transmitted by means of the mechanical clutcht to a gearing system 22, comprising'g'ears 22a, 221); 23,0 and a toothed rack 23l to zwhich the"elastic-element t is connected. This toothed rack, oneone side has: a'nose "23a whichenga'gesawith-a locking-pawl 8, and on the dtherlside, a thrustielement l which works'lever'iiil in such-adirectionthat it causes the disengagement :iori a known displacement: of :the toothed rack corresponding to a fixed stored quantity of energy in elastic element 4. On account of its elasticity, the thrust element 9 yields under the action of the thrust element 1. Of course, the motor 5 may be (and this cannot in any way afiect the field of the invention) an auxiliary motor, or else may be constituted by a motion gear on the propulsion motor of the aircraft.

Having now particularly described and ascertained the nature of my said invention and in what manner the same is to be performed, I declare that what I claim is:

1. :Inaircraft landing gear having an undercarriage a first energy accumulator for raising said undercarriage to its up position from its down position, motor means, means for connecting and disconnecting said first accumulator to said motor to store effective energy in the accumulatorgwhen the-under carriage reaches its down position, a second energy accumulator arranged to coact-with the .weight of the undercarriage for depressing the undercarriage to its down position, said second accumulator being arranged to be energized by the rising of the undercarriage from its down position to its up positionylocking means for locking-the undercarriage in the 'dOWIl position, and control means comprising a member operated by the undercarriage in the down position of the'latter for urging said connectingand disconnecting means toward connecting position.

2. A landing gear according to clairn l', wherein saidponnecting and disconnecting means comprises clutch'means, said control means further comprising gear and rack means effectively connected between said clutch means and said first accumulator.

' 3. A landing gear according to claim 1, wherein said second energy-accumulator comprises a spring connected to and between the landing gear and a 'fixecl point on the aircraft.

.4.:: An aircraft landing gear accordingrtoclaim 1, wherein :sa'i'd control means comprises another member operatediby said-first accumulator and connected. .to said connecting and disconnecting means whereby. the last mentioned "means is operatedito' disconnect the motor mean's from 'said first aocumulator'when sufficient energy-has been stored therein to 'raise the undercarriage.

5; In an aircraft-landing gear havingan undercarriage swingable between up and down positions, a firstIaccumuIatQr arranged to coa'ct with the weight of the' un'dercarriage to' depress the undercarriage from the up to the down" position, first locking -means for locking the undercarriage as it reaches the. down position, said=first accumulator being energized by raising the undercarriage from' 'the 'down "to its up position; a second accumulator. connected to said undercarriage for raising-said undercarriage from its down' to its upposition; motor means, clutchmeans for connecting said motor means to energizes-aid second accumulator; and first control means operated by the undercarriage to engage the clutch means as theundercarriage reaches its down position so-as to permit said 'motor' means" to energize said second accumulator, second control means operat'edby said-second accumulator for disengaging said clutch means as a' predetermined'suflicient amount tof energyto raise the undercarriage to its up position is stored in said second accumulator-,asecond locking means for locking-said second accumulator in the position thereof corresponding to; :the up ;-position 'of the undercarri ageg-said secqnd locking means being releasable to permit 5 I 6 said flrstaccumulator and the weight of the REFERENCES CITED undercarriage to depress the undercarriage to the down position. The following references are of record in the 6. A landing gear according to claim 1, wherein fil f t p t said connecting and disconnecting means com- UNITED STATES PATENTS prises electrlcally operated clutch means, means energizing said clutch including an electrical cir- Number Name Date cuit involving a first switch arranged to be closed 1,503,297 094151834115 July 1924 upon the release of the landing gear from its 2,224,431 Laramie 10, 1940 elevated position, and a second switch arranged 10 TENT to be closed by the movement of the landinggear FOREIGN PA 8 to its down position. Number Country Date 851,143 France Sept. 25, 1939 HENRI LONGEPIERRE. 

